OBJECTIVES: To identify whether patients using Actiq, an oral lozenge formulation of the powerful opioid fentanyl, have any evidence of cancer according to administrative claims records. The Food and Drug Administration has approved Actiq for breakthrough cancer pain and patients without such a diagnosis should therefore be considered off-label. METHODS: Pharmacy claims spanning the dates 2002 until 2005 from two large Midwestern and Southern health plans were used to identify patients receiving at least one Actiq prescription according to National Drug Codes. All medical claims for these patients were then searched for any primary or benign cancer diagnosis to identify whether the population potentially qualified for use of the drug according to Food and Drug Administration labeling. RESULTS: Of 1,481 patients identified with Actiq, only 399 (26.9%) had any evidence of cancer. The remaining 1,082 patients (73.1%) potentially received Actiq in an off-label setting. By year, the ratio of on versus off-label users was essentially unchanged from 2002 through 2005. However, the total number of users identified by year doubled from 220 in 2002 to 439 in 2005. CONCLUSION: The majority of Actiq prescriptions may be off-label. Given that the drug is a powerful, habit-forming opioid, these data suggest that the use of this drug should be considered for specific utilization review by insurers. These data also track recent evidence indicating that the use of these drugs has increased rapidly in recent years. Future work should examine whether off-label use of Actiq may be related to patient copay or other benefit design characteristics.